In recent years, active studies have been carried out on a technique of collecting thermal energy generated as a result of traveling of a vehicle, and converting the collected thermal energy to, for example, electric energy for effective use.
For example, Japanese Patent Application Laid-Open (kokai) No. H11-220804 shows a regeneration brake apparatus comprising a brake caliper which presses a brake pad against a rotation portion to thereby effect braking, a heat pipe connected to the brake caliper, a thermoelectric conversion element connected to a heart radiation end of the heat pipe, a radiator connected to a cooling side surface of the thermoelectric conversion element, and a battery connected to the thermoelectric conversion element. In this regeneration brake apparatus, friction heat generated as a result of braking is transmitted to a heating surface of the thermoelectric conversion element via the heat pipe, and a cooling surface of the thermoelectric conversion element is cooled by the radiator. By virtue of this configuration, the thermoelectric conversion element generates electric power in accordance with a temperature difference between the heating side and the cooling side, and the generated electric power is stored in the battery.
Also, for example, Japanese Patent Application Laid-Open (kokai) No. 2004-282851 discloses an in-wheel generator mechanism in which a Peltier element generates electric energy (electric power) by making use of a temperature gradient produced by heat generation at a bearing assembled into a wheel hub of a car and heat radiation at a wheel of the car. In this in-wheel generator mechanism, electric power generated by the Peltier element is used to drive a sensor system.
Furthermore, for example, Japanese Utility-Model Application Laid-Open (kokai) No. H4-17527 shows a brake oil cooling apparatus in which a thermoelectric element for cooling which exhibits a cooling action upon supply of electric power thereto is disposed near a flow path of brake oil; a thermoelectric element for electricity generation which converts heat to electric power is provided at a heat generation portion of an automobile; and electric power is fed from the thermoelectric element for electricity generation to the thermoelectric element for cooling. In this brake oil cooling apparatus, since electric power converted from heat by the thermoelectric element for electricity generation is supplied to the thermoelectric element for cooling, the thermoelectric element for cooling cools brake oil.
Moreover, for example, Japanese Patent Application Laid-Open (kokai) No. 2005-341700 discloses a thermoelectric generation apparatus which uses hot cooling water flowing out of an engine as a high-temperature-side heat source, and uses cooling water having passed through a radiator as a low-temperature-side heat source, and in which a thermoelectric element generates electricity by making use of a temperature difference between the high-temperature-side heat source and the low-temperature-side heat source. In this thermoelectric generation apparatus, since the high-temperature-side heat source and the low-temperature-side heat source can be secured stably, the thermoelectric element can generate electric power efficiently. The generated electric power is charged into a battery or used for operating various auxiliary devices around the engine.